This invention relates generally to lens design, and in particular to a zoom lens for use in a camera.
Compact, reasonably priced zoom lens for cameras are known. For example, U.S. Pat. No. 5,473,473 discloses a zoom lens having two plastic lens elements. The zoom lens includes a positive power lens element, a negative power lens element, and an aperture stop. While the zoom lens disclosed in U.S. Pat. No. 5,473,473 works extremely well for its intended purpose, plastic lenses having strong power are susceptible to a thermal reaction when exposed to changes in environmental operating conditions. This can cause a shifting of the image plane of the zoom lens relative to the rear (commonly referred to as last, etc.) element of the zoom lens.
As such, there is a need for a reasonably priced thermally stable (neutral, etc.) zoom lens that reduces shifting of the image plane relative to the rear element of the zoom lens caused by a thermal reaction of a plastic lens.
According to a feature of the present invention, a zoom lens includes, in order from an object side, a first lens group having a first lens element and a second lens element; and a second lens group having a third lens element. The zoom lens satisfies the following condition: |xcfx861|/xcfx86w less than 0.003, where xcfx861 is a power of the first lens element and xcfx86w is a power of the zoom lens in a wide angle position.
According to another feature of the present invention, a zoom lens includes, in order from an object side, a first lens group having a first lens element and a second lens element; and a second lens group having a third lens element. The zoom lens satisfies the following condition: |xcfx861|/xcfx86w less than 0.08, where xcfx861 is a power of the first lens element and xcfx86w is a power of the zoom lens in a wide angle position.
According to another feature of the present invention, a zoom lens includes, in order from an object side, a first lens group having a first lens element and a second lens element with the first lens group having a power and the second lens element having a power; and a second lens group having a third lens element, wherein the power of the first lens group is substantially equal to the power of the second lens element.